This invention relates to a system for monitoring and controlling the consumption of electrical energy and the peak demand for electric power.
Under many electrical utility company rate structures, the billing charge for electricity supplied to an installation is calculated on the basis of a two-part formula: a consumption charge based upon the total Kilowatt-hours of electrical energy consumed during the billing period; and a demand charge based upon the maximum kilowatt capacity or "peak demand" required during the billing period. The "peak demand" is the highest demand maintained over a continuous interval of time specified by the utility, typically 15 to 30 minutes. Thus the billing charge for electricity for an installation can be reduced both by decreasing the total energy consumption over the billing period and by decreasing the peak demand for electrical power.
In many installations, and particularly in commercial installations such as restaurants, stores, factories, hospitals and the like, much of the electrical equipment is thermostat-controlled, and cycles on and off at the command of its own thermostat. As a consequence, certain electrical equipment, such as restaurant air conditioners, refrigerators, cooking equipment and the like, are often operated simultaneously regardless of the time of day or the changing requirements of the particular installation. Moreover, when most or all of the equipment in an installation is "on" at the same time, the electrical demand rises toward its maximum, resulting in an increased demand charge in the electrical billing.
It is an object of the present invention to provide a relatively low cost system for monitoring and controlling the consumption of electrical energy and the peak demand for electrical power.
It is a further object of this invention to provide a control system which is easily connected to an existing electrical supply system with little rewiring.
It is another object of this invention to provide a control system which can be programmed to automatically limit the instantaneous power consumption of an installation.
It is still another object of this invention to provide a control system which can be programmed to automatically limit the instantaneous power consumption in accordance with the time of day and the required need of the facility.
It is a still further object of this invention to provide a control system which can control the instantaneous electrical power consumption of an installation at no detriment or loss of efficiency to the overall function of the installation.